1Monster Minds

2While I was still a graduate student at Princeton, I worked as a research assistant under John Wheeler. He gave me a problem to work on, and it got hard, and I wasn't getting anywhere. So I went back to an idea that I had had earlier, at MIT. The idea was that electrons don't act on themselves, they only act on other electrons.

3There was this problem: When you shake an electron, it radiates energy, and so there's a loss. That means there must be a force on it. And there must be a different force when it's charged than when it's not charged. (If the force were exactly the same when it was charged and not charged, in one case it would lose energy, and in the other it wouldn't. You can't have two different answers to the same problem.) The standard theory was that it was the electron acting on itself that made that force (called the force of radiation reaction), and I had only electrons acting on other electrons. So I was in some difficulty, I realized, by that time. (When I was at MIT, I got the idea without noticing the problem, but by the time I got to Princeton, I knew that problem.)

4What I thought was: I'll shake this electron. It will make some nearby electron shake, and the effect back from the nearby electron would be the origin of the force of radiation reaction. So I did some calculations and took them to Wheeler.

5Wheeler, right away, said, "Well, that isn't right because it varies inversely as the square of the distance of the other electrons, whereas it should not depend on any of these variables at all. It'll also depend inversely upon the mass of the other electron; it'll be proportional to the charge on the other electron." What bothered me was, I thought he must have done the calculation. I only realized later that a man like Wheeler could immediately see all that stuff when you give him the problem. I had to calculate, but he could see.

6Then he said, "And it'll be delayed ­­ the wave returns late ­­ so all you've described is reflected light."

7"Oh! Of course," I said.

8"But wait," he said. "Let's suppose it returns by advanced waves ­­ reactions backward in time ­­ so it comes back at the right time. We saw the effect varied inversely as the square of the distance, but suppose there are a lot of electrons, all over space: the number is proportional to the square of the distance. So maybe we can make it all compensate."

9We found out we could do that. It came out very nicely, and fit very well. It was a classical theory that could be right, even though it differed from Maxwell's standard, or Lorentz's standard theory. It didn't have any trouble with the infinity of self­action, and it was ingenious. It had actions and delays, forwards and backwards in time ­­ we called it "half­advanced and half­retarded potentials." Wheeler and I thought the next problem was to turn to the quantum theory of electrodynamics, which had difficulties (I thought) with the self­action of the electron.

10We figured if we could get rid of the difficulty first in classical physics, and then make a quantum theory out of that, we could straighten out the quantum theory as well.

11Now that we had got the classical theory right, Wheeler said, "Feynman, you're a young fella ­­ you should give a seminar on this. You need experience in giving talks.

12Meanwhile, I'll work out the quantum theory part and give a seminar on that later. " So it was to be my first technical talk, and Wheeler made arrangements with Eugene Wigner to put it on the regular seminar schedule.

13A day or two before the talk I saw Wigner in the hall. "Feynman," he said, "I think that work you're doing with Wheeler is very interesting, so I've invited Russell to the seminar." Henry Norris Russell, the famous, great astronomer of the day, was coming to the lecture!

14Wigner went on. "I think Professor von Neumann would also be interested." Johnny von Neumann was the greatest mathematician around. "And Professor Pauli is visiting from Switzerland, it so happens, so I've invited Professor Pauli to come" ­­ Pauli was a very famous physicist ­­ and by this time, I'm turning yellow. Finally, Wigner said, "Professor Einstein only rarely comes to our weekly seminars, but your work is so interesting that I've invited him specially, so he's coming, too." By this time I must have turned green, because Wigner said, "No, no! Don't worry! I'll just warn you, though: If Professor Russell falls asleep ­­ and he will undoubtedly fall asleep ­­ it doesn't mean that the seminar is bad; he falls asleep in all the seminars. On the other hand, if Professor Pauli is nodding all the time, and seems to be in agreement as the seminar goes along, pay no attention. Professor Pauli has palsy." I went back to Wheeler and named all the big, famous people who were coming to the talk he got me to give, and told him I was uneasy about it.

15"It's all right," he said. "Don't worry. I'll answer all the questions." So I prepared the talk, and when the day came, I went in and did something that young men who have had no experience in giving talks often do ­­ I put too many equations up on the blackboard. You see, a young fella doesn't know how to say, "Of course, that varies inversely, and this goes this way. . ." because everybody listening already knows; they can see it. But he doesn't know. He can only make it come out by actually doing the algebra ­­ and therefore the reams of equations.

16As I was writing these equations all over the blackboard ahead of time, Einstein came in and said pleasantly, "Hello, I'm coming to your seminar. But first, where is the tea?"

17I told him, and continued writing the equations.

18Then the time came to give the talk, and here are these monster minds in front of me, waiting! My first technical talk ­­ and I have this audience! I mean they would put me through the wringer! I remember very clearly seeing my hands shaking as they were pulling out my notes from a brown envelope.

19But then a miracle occurred, as it has occurred again and again in my life, and it's very lucky for me: the moment I start to think about the physics, and have to concentrate on what I'm explaining, nothing else occupies my mind ­­ I'm completely immune to being nervous. So after I started to go, I just didn't know who was in the room. I was only explaining this idea, that's all.

20But then the end of the seminar came, and it was time for questions. First off, Pauli, who was sitting next to Einstein, gets up and says, "I do not sink dis teory can be right, because of dis, and dis, and dis," and he turns to Einstein and says, "Don't you agree, Professor Einstein?"

21Einstein says, "Nooooooooooooo," a nice, German­sounding "No," ­­ very polite.

22"I find only that it would be very difficult to make a corresponding theory for gravitational interaction." He meant for the general theory of relativity, which was his baby. He continued: "Since we have at this time not a great deal of experimental evidence, I am not absolutely sure of the correct gravitational theory." Einstein appreciated that things might be different from what his theory stated; he was very tolerant of other ideas.

23I wish I had remembered what Pauli said, because I discovered years later that the theory was not satisfactory when it came to making the quantum theory. It's possible that that great man noticed the difficulty immediately and explained it to me in the question, but I was so relieved at not having to answer the questions that I didn't really listen to them carefully. I do remember walking up the steps of Palmer Library with Pauli, who said to me, "What is Wheeler going to say about the quantum theory when he gives his talk?"

24I said, "I don't know. He hasn't told me. He's working it out himself." "Oh?" he said. "The man works and doesn't tell his assistant what he's doing on the quantum theory?" He came closer to me and said in a low, secretive voice, "Wheeler will never give that seminar."

25And it's true. Wheeler didn't give the seminar. He thought it would be easy to work out the quantum part; he thought he had it, almost. But he didn't. And by the time the seminar came around, he realized he didn't know how to do it, and therefore didn't have anything to say.

26I never solved it, either ­­ a quantum theory of half­advanced, half­retarded potentials ­­ and I worked on it for years.